The present invention relates to lens design for electron emitters, particularly those electron emitters used in mass storage and display devices often incorporated in many electronic devices.
Computing technology continues to become less expensive while providing more capability. To allow computing technology to continue these positive trends, peripheral devices such as mass storage devices and display devices must continue to advance. Much criticism has been voiced in the trade press about the lack of mass storage devices such as disk drives, CD-ROMs, and DVD drives, to name a few, to keep up with the advancing speed of the microprocessors found in contemporary personal computers. Hard disk drives, for example, have been able to increase the storage density tremendously over the last decade but are now encountering physical limitations that prevents further progress. Although some hard disk drives have been miniaturized to operate with portable devices, the high power requirements still limit longer term battery operation. A more energy efficient, high density storage device is needed.
Display devices, such as LCD monitors have had difficulty in fulfilling demand due to the complexity of manufacturing them with near-zero defects. Further, the use of passive LCD technology has required the addition of backlights to allow for viewing in different ambient light conditions. These backlights require additional power thereby further limiting long term battery operation.
Electron beam technology has been present for many years in consumer products such as television (TV) tubes and computer monitors. These devices use what is known as hot cathode electrodes to create a source of electrons that are directed to and focused on the viewing screen. While research has taken place in a number of new technological fields, the field of cold cathode electron emitters such as spindt-tips and flat emitters has attracted the attention of many manufacturers. Several problems exist in converting this cold cathode technology to products. One such problem is the creation of an electron focusing structure that can be used in multiple applications that require a high density of emitting devices such as with mass storage and display devices. Usually, these applications require a high voltage potential between the electron-generating source (commonly called a cathode) and the media or viewing surface (commonly called an anode). When making compact devices, however, only a very short distance will separate the anode and cathode. This short distance makes it difficult to achieve a consistent tight focus of the electrons from the cathode source onto the anode. If a consistent tight focus is achievable, higher storage densities are possible because of smaller bit distances. Because the anode and cathode are held at differentially high voltage potentials, an electrostatic force created by the high voltage potential creates an attractive force between them. This attractive force creates additional problems, especially with movable components which must overcome this force, such as the media surface mass storage devices. In fact, a motor controlling the media surface must consume additional power, thereby affecting battery life in portable products. In display devices, this unwanted force could create undesired flexing or torsional stress. Unless this undesirable attractive force is reduced or eliminated, the use of cold cathode electron emitting technology may be delayed. Therefore, a need exists for a new lens structure that minimizes the attractive force between the anode and cathode structures while also maintaining tolerance to manufacturing process variations.
An electron lens is used for focusing electrons from a cathode to an anode. The lens includes a first conductive layer with a first opening at a first distance from the cathode. The first conductive layer is held at a first voltage. The lens also includes a second conductive layer with a second opening at a second distance from the first conductive layer and a third distance from the anode. The second conductive layer is held at a second voltage substantially equal to the voltage of the anode. The first and second openings are chosen based on the first voltage, the second voltage, the first distance, the second distance and the third distance. The force created between the cathode and anode is minimized by the structure of the lens.